Improve error message if the function hashmap is not detected

[montyly]

echidna/lib/Echidna/Solidity.hs

Lines 349 to 361 in 0378721

	prepareHashMaps cs as m =
	let
	(hm, lm) =
	( Map.unionWith NEE.union (filterHashMap not cs m) (filterHashMap id as m)
	, filterHashMap id cs m )
	in
	if | Map.size hm > 0 && Map.size lm > 0 -> (hm, Just lm) -- Usual case
	| Map.size hm > 0 && Map.size lm == 0 -> (hm, Nothing) -- No low-priority functions detected
	| Map.size hm == 0 && Map.size lm > 0 -> (m, Nothing) -- No high-priority functions detected
	| otherwise -> error "Error processing function hashmaps"
	where
	filterHashMap f xs =
	Map.mapMaybe (NE.nonEmpty . NE.filter (\s -> f $ (hashSig . encodeSig $ s) `elem` xs))

If the user provides a wrong filterFunctions, echidna crashes and the error message is not really clear:

We should change Error processing function hashmaps to something like Please verify the "filterFunctions" option or something like that, and ideally shows the ones that not found

[ggrieco-tob]

Good catch, we should fix this

[ggrieco-tob]

This should be fixed in #1258